Virtually all cultures around the world originally had traditions which incorporate regular fasting. In The End of Alzheimer's Program: The first protocol to enhance cognition and reverse decline at any age (2020), author Dale E. Bredesen, MD writes:
We're going to discuss fasting before we begin recommending specific foods. It's that important. [. . .] Not only has fasting been a historical part of the evolution of mankind, as an adaptation to food scarcity, it's also been incorporated into all of the major religions since their inception, both for the clarity of mind and the many health benefits. Most important for the purposes of our approach, fasting promotes the restoration of insulin sensitivity, which leads to an improvement in cognition. In our modern era, nonstop access to refined, sugary, processed, chemical-laden food leads to insulin resistance and metabolic inflexibility, whereby the source of fuel is limited to glucose, without the ability to utilize fats or their derivative ketones. Insulin resistance is central to the epidemic of chronic disease, including Alzheimer's. [. . .] This can be achieved in different ways. Some have early dinners, light dinners, or skip dinner. Alternatively, skipping breakfast is easier for others. Your home, work, and social demands along with your unique circadian rhythm can help guide the best fasting period for you. 93 - 94.
Regarding the centrality of this concept of insulin resistance, Dr. Bredesen says elsewhere in the text:
The bottom line is simple: We humans are not constructed to eat the amount of sugar and starch that we currently consume, any more than we are built to flap our arms and fly -- so we crash when we try either one of those (the crash just takes longer with sugar and starch, and includes hypertension, high cholesterol, diabetes, heart disease, strokes, advanced aging, arthritis, and dementia). 79
and:
Simple carbohydrates, such as sugar, starch, and processed foods, demand high insulin production -- more than our bodies are designed to produce. Having such high insulin levels causes our cells to scream: "Enough, turn down the volume!" eventually creating resistance to the effects of insulin. This means that not only will your cells not handle sugar as well (and reduced use of glucose in parts of the brain is characteristic of Alzheimer's), they also won't have the survival effect of insulin in the brain -- yes, insulin is a wonderful trophic factor for your brain cells, meaning that it keeps them alive. So it's little wonder that turning down the response to insulin is an important contributor to the very neurodegenerative process that occurs in Alzheimer's -- in fact, brain insulin resistance is present in almost all cases of Alzheimer's. 78 - 79.
Thus, the fact that fasting helps to (among other things) restore insulin sensitivity becomes extremely important, especially now that the modern western diet has caused insulin resistance to become an epidemic, with severe impact on human health (Dr. Bredesen notes that in 1976, about 5 million Americans were diagnosed as diabetic -- whereas today the number is over 100 million).
Dr. Bredesen's book emphasizes as one of its central points that Alzheimer's is an extremely complex disease, with multiple causes (which is why it resists a simple "silver bullet" cure), but the fact that nearly all cases of Alzheimer's involve brain insulin resistance surely indicates that insulin resistance (which is aggressively on the rise due to the disastrous change in food quality and ingredients and in eating habits during the modern era) plays a critical role.
The fact that all traditional cultures practice regular fasting, and that ancient wisdom from many different traditions all describe fasting as important, should give us all the additional incentive we need to consider incorporating this practice into our lives.
